Phone and Voice Node

This node is actually two small boxes. One houses the text to speech converter, and the other the various phone interfaces.

Text to Speech Converter

This unit was purchased from a commercialy company called RC systems. I found their add in the back of Circuit Cellar Ink. I wanted a unit that did not have a prerecorded vocabulary like the DigiTalker DT1050 from National Semiconductor. The RC Systems unit can accept a serial or parallel (PC printer) port type of interface. I decided to wire up the parallel port version because it allows the most flexibility. The speech quality is quite good, but one can definitely tell that it is synthetic. The box has a speaker output, and the output is also routed to one of the unused pins on the parallel port connector. Another pin on this port also controls an internal relay that switches the destination of the spoken sound. This allows the phone interface to inject the sound into the phone line, or allow it to be broadcast by speaker.

The unit was about $150 from RC Systems in Everett, WA.

The Phone Interface

The phone interface is capable of the following: I used the Caller ID decoder kit from the (now defunct) ITU to receive the name and number of the caller. The DTMF generation uses the PWM output of the PIC to produce the dual tone waveform, and the DTMF decoding is done by a dedicated chip.

With these functions, the central controller can give the caller a menu of options and decode which selection he/she desires. This will make better control possible of the system by phone. In this manner, the entire system can be controlled and configured using any phone in the world.

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